For example, three kinds of phosphor picture elements for coloring in red, green, and blue are formed on a phosphor surface of a glass panel inner surface of a cathode ray tube. These picture elements are regularly arranged in a dot or strip manner via a photo-adsorption film which is called a black matrix. In a case where such phosphor picture elements are formed by coating, a liquid coating apparatus is used.
The manufacture of the phosphor surface will be described as follows. First, a photosensitive resin film is formed on a glass panel inner surface of a cathode ray tube. At positions for forming phosphor picture elements in a portion where the photosensitive resin film is formed, a phosphor forming section is manufactured through photo-reactive material coating, exposure, and development. The photolithography technique is used for manufacturing the phosphor forming section. Next, a phosphor suspension (hereinbelow called a slurry) is coated on the panel inner surface. A phosphor forming section of a specific color is manufactured on request through the similar photolithography technique. The coating for forming the phosphor surface of the cathode ray tube is mainly carried out by rotary coating in which the slurry is coated on the panel while rotating the panel.
Such rotating coat is described below. First, a slurry in which a phosphor is suspended in a photosensitive resin is poured in the panel inner surface rotating at a lower speed. The poured slurry is gradually spread on the panel inner surface due to the inclination and rotation of the panel while the phosphor is precipitated. It is important to obtain a uniform coating film without coating nonuniformity in the phosphor coating process. For this purpose, there are already proposed a method of periodically changing the tilting angle of the panel in synchronization with the rotation period of the panel (for example, Japanese Unexamined Patent Publication No. 3-122944) and a method of carrying out the regular and reverse rotations of the panel (for example, Japanese Unexamined Patent Publication No. 5-101775).
Next, the panel is rotated at a higher speed to begin a superfluous liquid shaking-off process. In order to obtain a uniform coating film, it is important to set the tilting angle and the number of revolutions of the panel at the shaking-off operation. Then, there are already proposed a method of shaking-off the panel with the panel located upward diagonally (for example, Japanese Unexamined Patent Publication No. 55-57230) and a method of shaking-off the panel with the panel located downward diagonally (for example, Japanese Unexamined Patent Publication No. 59-186230).
In this process, a superfluous slurry is discharged outside of the panel. Next, the coating film is heated by an external infrared heater to dry it. Then, a shadow mask is set and subjected to exposure to ultraviolet light. The irradiation of the ultraviolet light allows a photo-crosslinking reaction to progress between a photosensitive resin and a photo-initiator while an exposed portion is insolubilized to water. After the exposure, the shadow mask is removed and a development is carried out by a hot water shower etc. to wash out an unexposed portion with water, thereby forming a phosphor pattern only at a required portion. Through the above processes, a phosphor surface of the cathode ray tube is completed.
On the other hand, in accordance with the change of Office Automation environment, requirements of a display for a cathode ray tube are variously changed from technical issues such as high fine accuracy, high luminance, and high contrast to ideal conditions of displays. Since it is difficult to see a screen of a cathode ray tube having a conventional curvature due to irregular reflection of external light, it has become increasingly necessary to make the configuration of the screen completely flat. Moreover, it is required to accomplish high luminance and high resolution at any portion in the central portion and in the peripheral portion of the cathode ray tube-use display due to the development of the Office Automation environment. In order to meet the requirement, as improved manners, for example, there is proposed a method in which during the forming of the phosphor surface, a slurry is linearly coated in a short time in a glass panel inner surface.
However, the above-described methods have the following issues.
(1) The conventional slurry coating methods require a slightly larger amount of the slurry in order to spread the slurry on the effective surface of the panel by adjusting the inclination and the number of revolutions of the panel. Therefore, an excessive amount of the slurry causes liquid spattering and inclusion of bubbles. There is a difference in film thickness due to the compulsive flow of the slurry from the central portion to the peripheral portion thereof by the inclination of the panel. PA1 (2) In a case where a slurry is linearly coated, it is very difficult to coat, with a laminar flow, the panel with a coating liquid discharged from a coating nozzle. Therefore, for example, there is caused a sidewise spattering phenomenon in which the liquid is discharged in a direction perpendicular to the nozzle sweep direction, so that uncoated portions are left on the panel inner surface.
Thus, an object of the present invention is to provide a superior novel nozzle for discharging liquid downward in a linear or curtain shape, provide a method for efficiently manufacturing the novel nozzle with high accuracy and provide a liquid coating method and apparatus for using the novel nozzle.
Another object of the present invention is to provide a cathode ray tube manufacturing method capable of forming a film of uniform thickness at low cost in a short time while suppressing the consumption of the necessary liquid.
Another object of the present invention is to provide a liquid coating nozzle and a cathode ray tube manufacturing method in which, by using the coating nozzle for linearly discharging downward a liquid and optimizing the coating schedule of phosphor surface formation (phosphor screen process), a phosphor surface having a coating pattern with a uniform quality can be implemented at a higher level, and a high-luminance cathode ray tube can be supplied.